High temperature end fitting and method of use
Inactive Publication Date: 2007-02-13
WELLSTREAM INT LTD
32 Cites 21 Cited by
AI-Extracted Technical Summary
Problems solved by technology
While functioning well, problems with the foregoing seals have arisen inside the end fitting where the flowline and end fitting are subjected to extreme fluctuations in temperature.
Repeated thermal cycling in the foregoing manner can result in a loss of seal integrity due to stress relaxation and creep of the barrier layer, followed by loss of comp...
Method used
[0021]Referring now to FIG. 1 of the drawings, there is illustrated a prior art end fitting designated 11 as disclosed, for example, in U.S. Pat. No. 5,639,128 incorporated herein by reference and available from commercial sources such as Wellstream, Inc. of Panama City, Fla. Briefly, the end fitting 11 comprises an annular body 13 adapted to receive a flexible flowline 12 which comprises an interior or carcass layer 14 and an exterior or barrier layer 16. An inner seal ring 18 presses against the external surface of the barrier layer 16. A sleeve 20 is received intervening between the carcass layer 14 and the barrier layer 16. As shown, the seal ring 18 is compressed between the interior wall surface of the annular body 13 and the exterior surface of the barrier layer 16. The barrier layer 16 may be of a relatively soft material, such as polymer. The polymer may be of many different types, such as polyvinylidene fluoride (PVDF). PVDF has a relatively high thermal expansion coefficient and softens when heated to its maximum service temperature. The sleeve 20 is placed below the seal ring 18 in order to provide increased support for the compressive forces that result from deforming the seal ring 18 into the barrier layer 16. The carcass layer 14 is typically steel or stainless steel. Because the carcass layer 14 and the body 13 are typically made from steel or stainless steel, their thermal expansion coefficient is much less that the barrier layer 16. Thus, under heat, the barrier layer 16 undergoes stress relaxation and the compressive forces transferred by the barrier are reduced. When cooled, the barrier layer 16 has lost some of its ability to recover and tends to shrink away from the seal ring 18, which could cause the connection to fail. On the other hand, some embodiments may not include a sleeve 20. In this case, the barrier layer 16 is supported by the carcass layer 14.
[0023]In operation, a plurality of bolts 42 radially positioned around the fitting 10 are tightened which causes the inner collar 24 to move closer to the annular body 22. As the inner collar 24 moves closer, the drive ring 34 is also moved closer to the annular body 22. The movement of the drive ring 34 causes an axial force on the seal unit 31 thereby driving the seal unit 31 further into the recess 30. The axial force on the seal unit 31 also causes the seal unit to deform in a radially inwardly direction towards the underling barrier layer 16. This deformation reduces the inside diameter of the housing ring 32 by forcing it onto a mating part of the en...
Benefits of technology
[0009]This invention relates to an improved seal construction for an end fitting in which an open end of flexible flowline is to be received. More specifically, the invention relates to such an end fitting in which a novel seal construction is provided capable of functioning to compensate, offset or be unaffected by the adverse effects...
Abstract
Embodiments of a system and method for sealing an end of a flowline to an end fitting are disclosed. Such methods include providing an end fitting housing having a bore, wherein a portion of the bore has a tapered inner surface, inserting an open end of a flexible pipe into the bore, the flexible pipe having an external layer, to create a tapered annular space between the tapered inner surface and the external layer, and positioning a ring into the tapered annular space such that the ring radially contracts upon the external layer causing the external layer to deform to create a seal.
Application Domain
Sleeve/socket jointsFluid pressure sealed joints +4
Technology Topic
EngineeringMechanical engineering +1
Image
Examples
- Experimental program(1)
Example
[0020]The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components, signals, messages, protocols, and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention from that described in the claims. Well-known elements are presented without detailed description in order not to obscure the present invention in unnecessary detail. For the most part, details unnecessary to obtain a complete understanding of the present invention have been omitted inasmuch as such details are within the skills of persons of ordinary skill in the relevant art.
[0021]Referring now to FIG. 1 of the drawings, there is illustrated a prior art end fitting designated 11 as disclosed, for example, in U.S. Pat. No. 5,639,128 incorporated herein by reference and available from commercial sources such as Wellstream, Inc. of Panama City, Fla. Briefly, the end fitting 11 comprises an annular body 13 adapted to receive a flexible flowline 12 which comprises an interior or carcass layer 14 and an exterior or barrier layer 16. An inner seal ring 18 presses against the external surface of the barrier layer 16. A sleeve 20 is received intervening between the carcass layer 14 and the barrier layer 16. As shown, the seal ring 18 is compressed between the interior wall surface of the annular body 13 and the exterior surface of the barrier layer 16. The barrier layer 16 may be of a relatively soft material, such as polymer. The polymer may be of many different types, such as polyvinylidene fluoride (PVDF). PVDF has a relatively high thermal expansion coefficient and softens when heated to its maximum service temperature. The sleeve 20 is placed below the seal ring 18 in order to provide increased support for the compressive forces that result from deforming the seal ring 18 into the barrier layer 16. The carcass layer 14 is typically steel or stainless steel. Because the carcass layer 14 and the body 13 are typically made from steel or stainless steel, their thermal expansion coefficient is much less that the barrier layer 16. Thus, under heat, the barrier layer 16 undergoes stress relaxation and the compressive forces transferred by the barrier are reduced. When cooled, the barrier layer 16 has lost some of its ability to recover and tends to shrink away from the seal ring 18, which could cause the connection to fail. On the other hand, some embodiments may not include a sleeve 20. In this case, the barrier layer 16 is supported by the carcass layer 14.
[0022]Referring to FIG. 2, there is an illustrated exemplary end fitting 10 incorporating one aspect of the present invention. Only the top half of the end fitting 10 is illustrated in FIG. 2 because the lower half is symmetrical with the top half. The end fitting 10 includes an annular body 22, an inner collar 24, a body ring 26 and a barrier sleeve 27. An interior surface of a counter-bore 28 in the body 22 and an exterior surface of a barrier layer 16 defines a wedge-like tapered recess 30. A tapered wedge-shaped seal unit 31 is positioned within the recess 30. In the illustrative embodiment, the seal unit 31 comprises a housing ring 32 and a housing drive-ring 34. The housing ring 32 may be made from a compressible metal, such as an annealed corrosion resistant metal, or a relatively hard polymer, such as polyphenylene sulfide or other deformable material compatible with fluids to be conveyed through the flowline. The housing ring 32 is generally wedge shaped so as to fit within the tapered recess 30. The housing ring 32 may have annular grooves defined on its interior surface, such as annular groove 37. A compressible seal 38, such as an elastomeric O-ring, may be positioned within the annular groove 37. Similarly, the housing ring 32 may have an annular groove 39 defined in its exterior surface. A compressible seal 40 may be positioned annular groove 39.
[0023]In operation, a plurality of bolts 42 radially positioned around the fitting 10 are tightened which causes the inner collar 24 to move closer to the annular body 22. As the inner collar 24 moves closer, the drive ring 34 is also moved closer to the annular body 22. The movement of the drive ring 34 causes an axial force on the seal unit 31 thereby driving the seal unit 31 further into the recess 30. The axial force on the seal unit 31 also causes the seal unit to deform in a radially inwardly direction towards the underling barrier layer 16. This deformation reduces the inside diameter of the housing ring 32 by forcing it onto a mating part of the end fitting which has a diameter smaller than that of the housing ring. This reduction in diameter of the housing ring 32 causes the surface of the barrier layer 16 to deform until all gaps between the barrier layer 16 and the seal unit 31 are eliminated. Flexible seals, such as the seals 38 and 40, may also be used to further reinforce the seal in the event of additional relaxation of the barrier layer 16. As a result of the foregoing, the seal, or seals provide a means to seal against an irregular surface which may, for example, be an extruded polymer tube such as the barrier of the received flowline. By forcing the housing ring 32 onto the polymer barrier surface 16, any surface irregularities are gradually reduced until the gaps between the housing ring and the barrier layer 16 are significantly reduced or eliminated. By reducing the gaps, the problem of potential extrusion of the flexible seals is also significantly reduced.
[0024]Alternative embodiments are shown in FIGS. 3 and 4. For brevity and clarity, a description of those parts which are identical or similar to those described in connection with the first embodiment will not be repeated here. Reference should be made to the foregoing paragraphs with the following description to arrive at a complete understanding of additional embodiment.
[0025]Referring now to FIG. 3, there is illustrated an end fitting 10 which includes a tubular insert 43 secured via bolts 44 to a body 49. A counter-bore 45 within the insert 43 accommodates receipt of the flexible pipe end 12 while an internally extending plastic cover 46 encircles the pipe at an entrance 48. Corrugated wires 50 are secured in epoxy 52 to maintain the structural integrity of the unit. Contained within the end fitting are the inner seal unit 31a with its housing ring 32a in a tapered recess 30a. In this embodiment, there is also an outer seal unit 53.
[0026]FIG. 4 is a detail view of the seal unit 31a and surrounding components from the embodiment illustrated in FIG. 3. An interior surface 41 of a counter-bore defined in the tubular insert 43 and the exterior surface of a barrier layer 16 defines a wedge-like tapered recess 30a. The tapered wedge-shaped seal unit 31a is positioned within the recess 30a. In the illustrative embodiment, the seal unit 31a comprises the housing ring 32a and a housing drive-ring 34a. The housing ring 32a is generally wedge shaped so as to fit within the tapered recess 30a. The housing ring 32a may have annular grooves defined on its interior surface, such as annular groove 37a. A compressible seal 38a, such as an elastomeric O-ring, may be positioned within the annular groove 37a. Similarly, the housing ring 32a may have an annular groove 39a defined in its exterior surface. A compressible seal 40a may be positioned in the annular groove 39a.
[0027]The operation of this embodiment is similar to the one described with reference to FIG. 2. When a plurality of bolts 47 are tightened, an inner collar 24a moves closer to the tubular insert 43. As the inner collar 24a moves closer, the drive ring 34a is also moved closer to the tubular insert 43. The movement of the drive ring 34a causes an axial force on the seal unit 31a thereby driving the housing ring 32a further into the recess 30a. The axial force on the seal unit 31a also causes the seal unit to deform in a radially inwardly direction towards the underling barrier layer 16. This reduces the inside diameter of the housing ring 32a and the drive ring 34a by forcing them onto a mating part of the end fitting which has a diameter smaller than that of the housing ring. This radial deformation causes the surface of the barrier layer 16 to deform until all gaps between the barrier layer 16 and the seal unit 31a are eliminated. Flexible seals, such as the seals 38a and 40a, may also be used to further reinforce the seal in the event of additional relaxation of the barrier layer 16.
[0028]Turning back to FIG. 3, one skilled in the art would realize that a similar situation occurs with respect to the outer seal unit 53. When a plurality of bolts 57 are tightened, an outer collar 59 moves closer to the body 49. As the outer collar 59 moves closer, the housing drive ring 55 is also moved closer to the body 49. The movement of the drive ring 55 causes an axial force on the seal unit 53 thereby driving the housing ring 54 further into the recess 56. The axial force on the seal unit 53 also causes the seal unit to deform in a radially inwardly direction towards the underling plastic cover 46. This reduces the inside diameter of the housing ring 54 and the drive ring 55 by forcing it onto the plastic cover 46 which has a diameter smaller than that of the housing ring. This radial deformation causes the surface of the plastic cover 46 to deform until all gaps between the plastic cover 46 and the seal unit 53 are eliminated. Flexible seals, such as the seals 38b and 40b, may also be used to further reinforce the seal in the event of additional relaxation of the barrier layer 16.
[0029]Some end fitting constructions may optionally also include a middle seal unit similar to and axially between inner and outer seal units 31 and 53. A detail of one such embodiment is illustrated in FIG. 5, which illustrates a middle seal unit 60. A housing ring 62 is wedged into a tapered recess 64 of a collar 66. Included within the housing ring 62 are opposite elastomeric seals 38c and 40c, which are similar to seals 38 and 40 described above. In this embodiment, a collar 67 can be used to drive the housing ring 62 into the tapered recess 64 when a plurality of bolts 69 are tightened. As illustrated, once the housing ring 62 is in place, the layer 16 deforms in a radially inward direction to accommodate the housing ring 62.
[0030]FIGS. 6 and 7 are section views of one embodiment of a housing ring, such as the housing ring 32, which could be used in various embodiments of the invention. Housing rings 54 and 62 could be of a similar configuration but with different diameters. In one embodiment, the housing rings 32, 54, and 62 may be formed of hard metal, having a cross sectionally tapered section as illustrated in FIG. 6. An outside surface 72 of the ring may include one or more annular grooves, such as the groove 37 in which to contain an elastomeric or flexible resilient seal, for instance an O-ring seal 38. Optionally, the housing rings can also include one or more internal grooves, such as groove 39, on the interior surface 78 for receiving an additional seal, such as an o-ring seal 40.
[0031]FIGS. 8 and 9 illustrate one embodiment of a drive ring, such as the drive ring 34. The drive ring 34 is tapered similarly as the housing rings and include side cuts 80 to permit a controlled collapse in the course of being forced into its receptive recess behind a seal ring.
[0032]The resilient seals 38, 40 can be O-ring, cup seal, X-ring, or other suitable shape that can be coupled to a housing ring 32, 54 and 62. On being forced into an encircling body with a matching taper but having a diameter smaller than that of the housing ring the inside diameter of the housing ring is caused to be reduced.
[0033]In this manner, sealing is provided and maintained against any irregular surface which may be an extruded polymer tube such as the barrier layer 16. By forcing the housing ring onto the polymer tube, any irregularities are gradually reduced until gaps between the housing ring and the polymer tube are eliminated. By eliminating the gaps, the potential for extrusion of the resilient seal is likewise eliminated.
[0034]Such construction can be used to seal high pressures since extrusion of the resilient seals is precluded. At the same time, the seal is superior to existing mechanical seals used in flexible pipes or hoses since mechanical seals require mechanical compression between the seal ring and the polymer layer. Moreover, the construction is not limited to the fluid sealing layer of flexible pipe since it can be readily applied to any extruded polymer layer of a flexible pipe or hose.
[0035]Significant for the foregoing is the use of a compressible metal seal housing ring or relatively hard polymer housing ring for the seal to deform the mating layer in such a way as to eliminate gaps. The design can be used to seal high pressures since extrusion of the resilient seal is avoided. Moreover, it is superior to existing mechanical seals used on flexible pipes or hoses since mechanical seals require mechanical compression between the seal ring and the polymer layer. Phenomena such as thermal expansion and creep can work to reduce or eliminate such compression.
[0036]At the same time, such construction is not limited to the fluid sealing layer of flexible pipe, since it can be readily applied to any extruded polymer layer in a flexible pipe or hose. By means thereof, a resilient seal applied directly to an extruded polymer layer, and housed in a metal housing which is forced onto the polymer layer to eliminate gaps, the previous problems associated with temperature induced seal failure in an end fitting is substantially if not completely eliminated. Furthermore, embodiments of the present invention work with flowlines which have barrier layers and flowlines which do not have barrier layers.
[0037]By the above description there is disclosed a novel seal construction for an end fitting that contributes significantly to the overall reliability of the end fitting per se. It achieves the intended result with only minor changes in construction so as not to contribute to any significant cost increase in manufacture of the overall end fitting. The virtues thereof can be readily appreciated by those skilled in the art.
[0038]Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense.
[0039]Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments. Accordingly, all such modifications are intended to be included in the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.
PUM
| Property | Measurement | Unit |
| Temperature | ||
| Flexibility | ||
| Deformation enthalpy |
Description & Claims & Application Information
We can also present the details of the Description, Claims and Application information to help users get a comprehensive understanding of the technical details of the patent, such as background art, summary of invention, brief description of drawings, description of embodiments, and other original content. On the other hand, users can also determine the specific scope of protection of the technology through the list of claims; as well as understand the changes in the life cycle of the technology with the presentation of the patent timeline. Login to view more.